The synthesis of di- and polycyclic systems composed of cyclopentane rings has been developed further, with particular emphasis upon elaboration of synthetic approaches to biologically active compounds of this type, and to deepened understanding of the mechanisms of the reactions utilized. Cooperation with the colleagues in India in the field of chemistry of morphine and codeine has been continued. Earlier studies on the chemistry of powerfully photosensitizing perylenequinones from certain molds has been continued. The complex stereochemistry of these mold metabolites presents unusual problems.